[master] c4b418a1c builtin: Minor polish

[Nils Goroll]

commit c4b418a1c797d38666f72bc0c9734000af5f69d5
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Wed Mar 3 11:21:44 2021 +0100

    builtin: Minor polish
    
    Only copy the host header if needed

diff --git a/bin/varnishd/builtin.vcl b/bin/varnishd/builtin.vcl
index eb7c9272a..8c7d2eb04 100644
--- a/bin/varnishd/builtin.vcl
+++ b/bin/varnishd/builtin.vcl
@@ -44,7 +44,7 @@ sub vcl_recv {
 }
 
 sub vcl_req_host {
-	if (req.http.host) {
+	if (req.http.host ~ "[[:upper:]]") {
 		set req.http.host = req.http.host.lower();
 	}
 	if (!req.http.host &&